package string;

import jdk.nashorn.internal.ir.IfNode;

import java.util.Scanner;

public class test4 {
    public static boolean Legal(char ch) {
        if(ch>='a'&&ch<='z'||ch>='0'&&ch<='9')
        {
            return true;
        }
        return false;

    }
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        String str=sc.nextLine();
        String str1=str.toLowerCase();
        char ch[]=str1.toCharArray();
        for(char row:ch){
            System.out.print(row+" ");
        }

        int index=str1.length()-1;
        int i=0;
        while (i<index){
            if (Legal(ch[i])==false){
                i++;
            }
            if (Legal(ch[index])==false){
                index--;
            }
            if (ch[i]==ch[index]){
                i++;
                index--;
            }
            else {
                System.out.println("不是回文字符串");
                return;
            }
        }
        System.out.println("是回文字符串");
    }
}
